1. Field of the Invention
The present invention relates to a camera film advancing apparatus of the type in which a film is transported through the engagement of a sprocket pawl with the film perforations, and is more particularly directed to improvements in reliability of the engagement in such film advancing apparatus and in simplicity of the film charging operation.
2. Description of the Prior Art
As a film advancing apparatus of the type mentioned above there has been known and widely used apparatus comprising biasing means by which a film pressing member is urged against the circumferential outer surface of a sprocket. At the time of film charge, the film pressing member is moved away from the circumference of the sprocket against the bias force so as to provide a space between the circumferential surface of the sprocket and the film pressing member into which a film is inserted. After the insertion of film into the space, the film pressing member is again returned to its original position in which it is pressed against the circumferential surface of the sprocket by the bias means. As a result, the portion of the film inserted into the space is also pressed against the circumferential surface of the sprocket through the film pressing member so that an engagement is established between the pawl of the sprocket and the perforation of film. The engagement established in this manner is so firm that no disengagement may occur even when the film becomes slack in its passage between the film cartridge and the sprocket.
Although the known apparatus described above can assure a good engagement between the sprocket and film, it has a disadvantage in that the operation involved therein is somewhat troublesome and complicated. Thus, the apparatus in question necessitates two different operations, that is, an operation for forcibly moving the film pressing member away from the circumferential surface of the sprocket and an operation for inserting the film into the formed space. The user must conduct these two separate operations every time the film is charged.